In a fuel cell system installed in, for example, a fuel cell vehicle, a high-pressure hydrogen tank is used as a fuel gas supply source. The high-pressure hydrogen tank is, in general, manufactured using a filament winding method. Specifically, in the filament winding method, a fiber impregnated with thermosetting resin is wound around an outer periphery of a liner (inner container) and then the resin in the wound fiber is thermally cured. As a result, a reinforcement fiber layer is formed on the outer periphery of the liner to thereby ensure the strength of the high-pressure hydrogen tank.
Since the filament winding method typically uses a fiber impregnated with low-viscosity resin, a terminal end (i.e., a winding end) of the fiber may not be able to be attached with sufficient strength to a winding surface, being a surface formed by the already-wound fiber, and may thus possibly be detached therefrom. In addition, the viscosity of resin is further lowered due to heat during thermal curing and the terminal end of the fiber will become easily loosened. Thus, at the end of winding, an operator has cut the fiber and tightly fixed, by tying or the like, the terminal end of the fiber onto the winding surface.
Another known method for handling the terminal end of fiber, different from the tying and fixing method above, is described in, for example, Patent Document 1 below. In this method, a double-faced tape is adhered to an inner surface of the terminal end of prepreg fiber and the terminal end of the fiber is adhered to the winding surface at the end of winding. In addition, a tank manufacturing method described in Patent Document 2 includes the steps of winding a fiber impregnated with resin by a predetermined number of windings and thermally curing the impregnating resin in the wound fiber to thereby form a reinforcement fiber layer. In the winding step, the terminal end of the fiber is inserted into the already-wound fiber using a jig. More specifically, the terminal end of the fiber is inserted so as to transverse the windings of the already-wound fiber forming the outermost layer in such a way as to hold the terminal end of the fiber between the outermost layer of the already-wound fiber and an inner layer of the outermost layer to thereby hold the terminal end of the fiber by several windings of the already-wound fiber.
However, the method of tying and fixing the terminal end by an operator's hand requires a lot of time and effort. In order to mass-produce tanks, it is desirable to improve the operability of the filament winding method by shortening the time taken for the winding step.
Furthermore, in the method using the double-faced tape in Patent Document 1 and the method of inserting the terminal end of the fiber into the already-wound fiber in Patent Document 2, a portion provided with the double-faced tape or a portion in which the fibers overlap one another as a result of the insertion of the fiber is bulged after thermal curing and is highly likely to cause irregularities to be formed on an outer surface of the resulting tank. Such irregularities not only degrade the appearance of the resulting tank as a finished product but also cause stress concentration and damage therein and further cause degradation of the strength of the reinforcement fiber layer. In addition, the techniques described in Patent Documents 1 and 2 require manual operations by a human and it is thus difficult to be automated.